If the connection to the ignitor is the press on type like what exists for auto spark plugs, one common problem is the internal part of the connection to the ignitors post is not clamping firmly enough. Even thu you can press it on and it seems tight, any minut loosness not felt via the feel test will cause the current to be inconsistant resulting in your type of problem. If you do have the post fitting as opposed to the blade type connection, crimp the fitting on the wire little so that the slip on connection is super tight. Regular pliers will do the job by squeezing the end of the wire. You can do this safely thru the insulating boot at the end of that connection. Just do not damage the covering rubber/plastic boot. Hope this helps.
